U.S. stock indexes are drifting lower as momentum slows for Wall Street after it rallied from a deep hole nearly all the way back to its all-time high set earlier this year. The S&P 500 was down 0.3% in early trading Tuesday.

U.S. stocks were mostly lower in choppy trading on Monday with market sentiment weakened by the downgrade of the federal government's perfect sovereign credit rating owing to its huge debt profile. Moody's slashed the U.